Magnetic lacquer dispersions generally consist of one or more magnetic pigments, abrasive (for example chromium oxide, Cr.sub.2 O.sub.3) and carbon black for regulating the surface conductivity of the magnetic recording materials produced using these magnetic lacquer dispersions. These solids are normally dispersed in a polymer binder in organic solvents using phospholipids as wetting agents and long-chain, saturated carboxylic acids as lubricants.
To produce magnetic lacquer dispersions by the batch process, the above-mentioned constituents are normally predispersed in a first step, for example using a laboratory dissolver or a toothed colloid mill, and then in a second step are dispersed in a non-continuous or continuous bead mill.
Magnetic lacquer dispersions may also be produced by two-stage processes which differ from the batch process described above in that parts of the liquid constituents and of the binder are added in a third process step known as "Auflackung"=(let down). The rest of the material to be ground is predispersed, as in the batch process, and then ground in a bead mill of suitable construction.
The magnetic lacquer dispersion thus obtained is used to coat carrier films from which magnetic recording supports for various applications are made. The quality of the magnetic lacquer dispersions produced in this way is critically determined by the type, quantity and method of incorporation of the wetting agents and lubricants in the dispersion.
The use of lecithins are wetting agents and carboxylic acids as lubricants in the production of magnetic lacquer dispersions is known from the literature, cf. for example JP-A No. 57-200 934 and JP-A No. 60-007 612. However, the magnetic lacquer dispersions thus obtained are not suitable for the production of magnetic recording supports having optimal properties.
Accordingly, the object of the present invention is to provide magnetic lacquer dispersions which do not have any of these disadvantages.